Modern vehicles have lots of electronics that operate functions such as the dashboard and warning lights. If the car is showing a 4WD light when it's not actually in 4WD, then there's an electrical glitch somewhere in the system.

But the fact that it occurs in tandem with a second fault (the incorrect speedo reading) makes us wonder if you're not looking at something as fundamental as a bad earth somewhere on the car. Electricity can't flow if the circuit isn't earthed, and this is a common source of problems like the one you're seeing. A good auto electrician should be able to sort both problems with simple test gear. If not, a scan of the vehicle's systems may throw up the answer.

Your owner's manual should give you a bit of insight here, but often, functions such as these can be turned on and off via menus within the car's infotainment system or its switchgear.

What's probably happened is that the car's battery has been disconnected at some point during the servicing procedure and the car has reverted to what's known as factory settings. If there's no provision for turning the warning buzzer back on, I'd take it back to the servicing workshop, as something has been altered to disable the buzzer.

I’ve hard of this before and it usually seems the cause has something to do with the wiring that controls these warning lights. It could either be a bad earth or a broken wire, but in most cases the symptoms are the same; a flashing 4WD indicator light when the vehicle is in two-wheel-drive. I’ve also heard of dud ABS sensors triggering the same, or similar, warning lights on the dashboard.

These vehicles use servos to engage four-wheel-drive (unlike older vehicles which used a manual lever pulled on by the driver) so there’s a level of electronics involved. And that always means potential problems as the cars age, particularly a vehicle that may have seen its share of rough stuff over the years.

The best advice is to have a Mazda specialist interrogate the on-board computer, at which point the car should give up all its dirty little secrets, including why it thinks it’s in four-wheel-drive when it’s not.